The animals were taken from the wild and reared as adults, which immediately makes one think “sperm storage.” The authors argue that the genetic similarity of the offspring rules this out. I think an obvious next step is to see if juveniles born in the lab without sex can be reared through an entire generation, and in turn produce more offspring without meeting males.

This is a bombshell. It suggests that asexual reproduction in crayfish is more common than thought, particularly when the P. clarkii paper is also hinting that they can do the same. From an evolutionary point of view, this would mean that the evolution of the completely asexual lineage of Marmorkrebs may not have been as insurmountable as it first appeared.

Several alien crayfish of North American origin have become established in Europe in recent decades, but their identification is often confusing. Our aim was to verify the taxonomic status of their European populations by DNA barcoding. We sequenced the cytochrome c oxidase subunit I (COI) gene fragment of individuals representing all American crayfish known from European waters, and compared the results with reference sequences from North America. Our results confirm the morphological identification of Orconectes juvenilis from a population in eastern France, and of the marbled crayfish (Marmorkrebs), i.e., a parthenogenetic form of Procambarus fallax, from south-western Germany. Sequences of most individuals of presumed Procambarus acutus from the Netherlands were similar to American P. cf. acutus, but one was divergent, closer to a sequence of a reference individual of P. cf. zonangulus. However, divergences among three American P. cf. zonangulus samples were also high, comparable to interspecific variation within cambarid species complexes. The divergence between O. immunis from Europe and America also reached values corresponding to those observed among distinct Orconectes species. Genetic variation in the American range of these crayfish should therefore be further studied. Our study shows that DNA barcoding is useful for the rapid and accurate identification of exotic crayfish in Europe, and also provides insights into overall variation within these taxa.

17 May 2011

I’m embarrassed to admit that once in a while, I wasn’t able to get to my own website on the first try.

If you live in North America and type in a domain name, what do you normally do after you get to the dot? You start typing “com”. It’s easy to forget about other domain names like “net” or “org” entirely.

But I won’t have that problem any more. And neither will anyone else. The Marmorkrebs website can now be reached by through Marmorkrebs.com.

Photo by RambergMediaImages on Flickr; used under a Creative Commons license.

10 May 2011

The origin of Marmorkrebs is still unknown. Hybridization of two species in aquaria has sometimes been tossed around as a potential hypothesis. It has some plausibility, given that almost every parthenogenetic vertebrate seems to trace back to a hybridization event. A new paper would seem to make the hybridization hypothesis slightly more plausible.

I’ve written before about whiptail lizards, the first multicellular animals I learned of that reproduced by parthenogenesis.

A paper in press by Aracely and colleagues describes the latest research on these animals: make a new, self-sustaining, hybrid from scratch. And the experiment was a success! The picture shows the hybrid in the middle of the two parental species. The hybrids have been reared through multiple generations in the lab, so this is not just a one-off event.